Supersolid quantum gases in a new dimension

Two-dimensional supersolid quantum gas produced in the laboratory for the first time.

Quantum gases are very well suited to study the microscopic consequences of interactions in matter. Today, scientists can precisely monitor individual particles in extremely cooled clouds of gas in the laboratory, revealing phenomena that cannot be observed in the everyday world. For example, the individual atoms in a Bose-Einstein condensate are completely delocalized. This means that the same atom exists at each point of the condensate at a given time.

Two years ago, the research group led by Francesca Ferlaino from the Department of Experimental Physics at the University of Innsbruck and the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences in Innsbruck has succeeded for the first time in generating super-solid states in ultra-cold. quantum gases of magnetic atoms. Magnetic interaction causes atoms to self-organize into droplets and organize in a regular pattern.

“Normally, you would think that each atom would be in a specific droplet, with no way to move between them,” says Matthew Norcia of Francesca Ferlaino’s team. “However, in the supersolid state, each particle is delocalized through all the droplets, existing simultaneously in each drop. So basically you have a system with a series of high density regions (the droplets) that all share the same ones. delocalized atoms.

This bizarre formation allows effects such as frictionless flow despite the presence of spatial order (superfluidity).

New dimensions, new effects to explore

So far, supersolid states in quantum gases have only been observed as a chain of droplets (along one dimension). “Together with theorists Luis Santos from Leibniz Universität Hannover and Russell Bisset in Innsbruck, we have now extended this phenomenon to two dimensions, giving rise to systems with two or more rows of droplets,” explains Matthew Norcia. This is not only a quantitative improvement, but also a crucial broadening of research perspectives.

“For example, in a two-dimensional supersolid system, we can study how vortices form in the hole between several adjacent droplets,” he says. “These vortices described in theory have not yet been demonstrated, but they represent an important consequence of superfluidity,” Francesca Ferlaino is already looking to the future. The experience now reported in the journal Nature creates new opportunities to delve deeper into the fundamental physics of this fascinating state of matter.

New field of research: supersolids

Predicted 50 years ago, supersolidity with its surprising properties has been extensively studied in superfluid helium. However, after decades of theoretical and experimental research, clear evidence of the supersolidity of this system was still lacking. Two years ago, research groups from Pisa, Stuttgart and Innsbruck independently succeeded for the first time in creating supersolids from magnetic atoms in ultra-cold quantum gases. The basis of the new and growing field of supersolids research is the strong polarity of magnetic atoms, whose interacting characteristics allow the creation of this paradoxical state of quantum mechanics of matter in the laboratory.

Reference: “Two-dimensional supersolidity in a dipolar quantum gas” August 18, 2021, Nature.
DOI: 10.1038 / s41586-021-03725-7

The research was financially supported by the Austrian Science Fund FWF, the Federal Ministry of Education, Science and Research and the European Union, among others.